Abstract

The population structure of Labeo dussumieri, an endangered and endemic cyprinid from
three riverine locations in the Western Ghats, India was investigated using allozyme, microsatellite
and RAPD markers. L. dussumieri samples were obtained from Meenachil, Manimala and Pamba
River basins, Kerala. Fourteen (46.7%) out of 30 allozyme loci, seven microsatellite loci and 12
RAPD Operon decamers gave polymorphic pattern. Six allozyme loci (AAT-2*, EST-4*, GLDH*,
GPI-2*, G6PDH* and LDH-2*) and three microsatellite loci (LdussG1, MFW19 and Bgon22)
exhibited consistent significant deviation from Hardy-Weinberg Equilibrium expectations in
different populations after probability level (P<0.05) was adjusted for sequential Bonferroni
correction. All the three marker types demonstrated concordant results and various estimates
revealed genetic variability within the subpopulations but surprisingly low level (= 0.0034 to
0.0081) of genetic differentiation among L. dussumieri from different river samples. AMOVA
analysis also indicated low differentiation among subpopulations. No evidence for a recent genetic
bottleneck was observed in L. dussumieri populations based on allozyme and microsatellite data
set analysis. Meenachil, Manimala and Pamba Rivers open in to the southern end of Vembanad
Lake in Kerala and are connected to each other in the lower reaches through an extensive network
of natural canals. Common ancestry in the prehistoric period; and possible mixing of fish
populations resulting in high gene flow across the rivers through the lake and interconnecting
canals could have been responsible for the lack of significant allelic heterogeneity among the
L. dussumieri populations. The stocks from the three rivers do not require different management
strategies and for propagation assisted river ranching programme of this species, large effective
breeding population can be developed by mixing individuals from three rivers